1. Field of the Invention
The present invention relates to a cold cathode ionization vacuum gauge having a discharge starting auxiliary electrode triggering discharge, a vacuum processing apparatus having the cold cathode ionization vacuum gauge, a discharge starting auxiliary electrode, and a method of measuring pressure using the cold cathode ionization vacuum gauge.
2. Description of the Related Art
A cold cathode ionization vacuum gauge triggers gas ionization by self-discharge between an anode and a cathode to measure the internal pressure of a vacuum container which constitutes a vacuum processing apparatus. There are known cold cathode ionization vacuum gauges: penning type, magnetron type, and inverted magnetron type, (refer to Japanese Patent Laid-Open No. H10-19711). In particular, the magnetron type and the inverted magnetron type have a structure in which electron-trapping efficiency is high and which enables a stable sustained discharge even in a high-vacuum region, thus being suitable for measurement in high-vacuum regions.
In a cold cathode ionization vacuum gauge, it is necessary to apply a high voltage thereto to trigger the gas ionization for starting the discharge. There is generated a delay, however, between the timing at which a high voltage is applied to the cold cathode ionization vacuum gauge and the timing at which a discharge current begins to flow due to the start of sustained discharge. The time delay affects the period of time before the start of measurement.
According to a cold cathode ionization vacuum gauge disclosed in Japanese Patent Laid-Open No. H06-26967, a cathode has a discharge-triggering means for directly irradiating electromagnetic radiation sufficient to cause the cathode to emit photoelectrons, thus shortens the period of time for discharge-triggering between the application of a voltage and the start of sustained discharge. According to a cold cathode ionization vacuum gauge disclosed in Japanese Patent Laid-Open No. 2008-304360, an ignition auxiliary tool for triggering discharge is provided at cathode side to shorten the period of time for discharge-triggering between the application of a voltage and the start of sustained discharge.
The cold cathode ionization vacuum gauge disclosed in Japanese Patent Laid-Open No. H06-26967, however, has a drawback of complicated structure of apparatus because the gauge separately has a glow lamp, an ultraviolet ray irradiation lamp, or the like as a means for triggering the discharge and has a circuit for the means. Regarding the cold cathode ionization vacuum gauge disclosed in Japanese Patent Laid-Open No. H06-26967, since the gauge gives high efficiency of trapping charged particles, the wall surface of container of the vacuum gauge is easily sputtered. Consequently, when the gauge is used for a long period of time, sputtered films or products stick to the lamp surface to impair the irradiation of ultraviolet rays. Consequently, the generation of photoelectrons which cause the start of discharge reduces, and thus triggering the discharge becomes difficult.
On the other hand, the cold cathode ionization vacuum gauge disclosed in Japanese Patent Laid-Open No. 2008-304360 has a drawback of short effective period of shortening the time of triggering discharge, thus shortening the life of the gauge owing to the presence of sputtered films and deposited films stuck to the surface of electrode resulted from long use period of the gauge, or owing to the presence of films generated from reaction with residual gases.